1. Field of the Invention
This invention relates generally to the field of universal secure housing arrangements for enclosing electronic circuit boards or the like. More particularly, this invention relates to a low cost housing for electronic circuit boards which may be configured in a variety of ways to accommodate a variety of circuit board configurations and requires no tools to assemble yet requires tools to disassemble.
2. Background of the Invention
In order to reduce the cost of housing various types of electronic equipment such as modems, multiplexers, encryption devices and the like it is frequently desirable to provide a single housing configuration which may be adapted to the needs of varying circuit board configurations. When it is possible to provide a common universal housing for a variety of electronic equipment, increased volume of purchase of the universal housing reduces the cost of producing such electronic equipment. In addition, inventory costs for maintaining stocks of a great variety of housings can be substantially reduced thereby further reducing product costs. It is also desirable to provide for ease of assembly of such a univeral housing by requiring that no tools be necessary to accomplish assembly. This goal is frequently contradictory to a desire to provide a degree of tamper resistance to the device. A degree of tamper resistance makes access to possibly hazardous voltages within the housing more difficult thus enhancing the safety of the electronic device and reducing the hazard of shock or fire.
In fact, product safety organizations such as the Canadian Standards Association (CSA) and Underwriter Laboratories (UL) have established standards for such enclosures. CSA's standard for data processing equipment for customer and commercial products C22.2 No. 154-M1983 and UL478 Standards for Information Processing and Business Equipment are two such standards for so called secured housings. It is advantageous for both safety and business considerations to enclose electronics devices inside housings which meet these types of specifications.
Several examples of fastening arrangements which are typically used to satisfy the requirements of such standards are ordinary screw fastener arrangements or quarter turn coin operated fasteners. Unfortunately, there are serious cost drawbacks in utilizing either of these common fastening arrangements. In the case of screw fasteners, although the part cost is nominal, the labor associated with assembling a screw assembled enclosure is considerable. In the case of quarter turn coin operated fasteners, parts cost is relatively higher and the degree of security obtained is somewhat limited due to the many types of devices (including coins) which can be used to open such fasteners. Additionally, serious damage to electronic circuits may occur due to short circuits if such metal fasteners are accidentally dropped or left inside such housings when reassembled.
While resilient latches of various arrangements have been used for assembling various types of plastic contains of the past, the present invention utilizes a resilient plastic latching arrangement which allows for inexpensive ABS type plastic to be used abundantly while providing a secure enclosure with exceedingly low parts and labor cost. In addition, the present invention provides for a high degree of tamper resistance.
The present invention also provides for ready adaptation to a great number of possible circuit board configurations including the capability of handling a plurality of circuit boards of varying sizes while largely avoiding the necessity for modification to the basic housing arrangement.